1. Field of the Invention
This invention relates to a radiation-sensitive resin composition comprising a solution of an alkali soluble resin and a radiation-sensitive compound dissolved in a solvent, which composition is sensitive to radiations such as ultraviolet rays, far-ultraviolet rays, X-rays, electron beams, molecular beams, gamma-rays, synchrotron radiations, proton beams and the like.
2. Description of the Invention
The resist compositions currently used in making integrated circuits comprises an alkali-soluble resin and a radiation-sensitive compound, and more specifically known are (a) positive type resist compositions comprising an alkali-soluble resin and a 1,2-quinonediazide compound and (b) negative type resist compositions comprising an alkali-soluble resin and an azide compound.
When these resist compositions comprising an alkali-soluble resin and a radiation-sensitive compound are exposed to a radiation through a mask and then subjected to development with a developer consisting of an aqueous alkaline solution, the exposed portions in the case of the positive type resist compositions or the nonexposed portions in the case of the negative type resist compositions are dissolved in the developer, whereby a resist pattern which is faithful to the mask and has a high resolution is obtained. Therefore, resist compositions comprising an alkali-soluble resin, which are excellent in resolution, have been often used in recent years during which higher integration of integrated circuits has been demanded.
However, resist compositions comprising a solution of an alkali-soluble resin and a radiation-sensitive compound in a solvent have the following drawbacks: When the resist compositions are filtered through a filter having a pore diameter of, for example, 0.2 .mu.m and then allowed to stand, it happens in some cases that fine particles which are too fine to observe visually are formed in the compositions, and when the compositions containing the resulting fine particles are further stored for a long period of time, precipitation comes to be observed. In such resist compositions, the fine particles have, in some cases, a particle diameter of at least 0.5 .mu.m. When a resist composition containing fine particles having such a large particle diameter is used to form a resist pattern of about 1 .mu.m on a wafer, the fine particles remain at the substrate portion where the resist is removed by development, resulting in a reduction of resolution. Further, when a substrate is etched through a resist pattern formed from a resist composition containing such fine particles, pin holes appear also at the substrate portion covered with the resist pattern, resulting in a reduction of yield in the manufacture of integrated circuits.